An electrochemical cell has been used as a backup power source of memories and a backup power source of clock functions in various types of small-sized electronic devices such as a cellular phone, a personal digital assistant (PDA) and a portable game machine. In recent years, there has been a growing demand for this type of electrochemical cell to be decreased in size and thickness. This is because an electronic device on which an electrochemical cell is mounted has been made smaller. Further, an electrochemical cell is commonly packaged by reflow soldering (a method in which a soldering cream-coated electrochemical cell is placed on a packaging substrate and heated together with a circuit substrate to effect soldering). For this reason, heat resistance is required for an electrochemical cell so as to withstand heat resulting from reflow soldering.
Conventional electrochemical cells are available mostly in the shape of a coin in which a cell case is crimped and sealed. Therefore, these cells are unable to effectively use a packaging area, which inhibits space saving. Further, on reflow soldering, terminals, etc., require welding in advance and the number of components and manufacturing steps are increased, resulting in a rise in cost.
Therefore, in order to solve the above-described type of problems, the tests have been conducted for an electrochemical cell substantially in the shape of a square (chip-shape) which is able to use a packaging area effectively. This chip-type electrochemical cell is different from a coin-shaped electrochemical cell and cannot be sealed by crimping a can (case). Therefore, such an electrochemical cell has been provided that a recessed container is welded on a sealing plate to internally seal electrodes, etc. (refer to Patent Document 1).